Pd–Bi bimetallic catalysts including polyvinylpyrrolidone surfactant inducing excellent formic acid oxidation reaction and direct formic acid fuel cell performance

PdBi bimetallic catalysts are synthesized while their catalytic activity and stability for formic acid oxidation reaction (FAOR) and direct formic acid fuel cell (DFAFC) performance are evaluated. According to investigations, Pd₂Bi₁/C catalyst including low Pd amount promotes oxygen desorption with enhancement in CO poisoning resistance. With that, indirect formic acid oxidation reaction (IFAOR) and its stability are improved. To further improve the FAOR, polyvinylpyrrolidone (PVP) surfactant is contained due to its amphiphilic property reducing Bi aggregation. To determine optimal amount of the PVP, analysis using TEM and XPS is performed and the results are verified by density functional theory (DFT). According to TEM, in 0.22 PVP-Pd₂Bi₁/C catalyst, PdBi has small size (∼5 nm) and is well-dispersed with widest E_d- E_F of 3.85 eV, proving the catalyst induces effective CO-poisoning resistance and less Bi aggregation. These results are also compatible with trend in FAOR measured by cyclic voltammogram (CV). Even long-term stability, the catalyst maintains catalytic activity well. The best performance of DFAFC using the catalyst (32.7 mW cm⁻²·Pd_g⁻¹) indicates that 0.22 PVP- Pd₂Bi₁/C is excellent catalyst for FAOR and DFAFC performances.